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4.
BIOLOGICAL FUNCTIONS OF LIPIDS• Energy Source – When oxidized, each gram of fat releases 9 kcal of energy, or more than twice the energy released by oxidation of a gram of carbohydrate• Energy Storage – In the form of triglycerides (TAG) in adipocytes• Cell Membrane Structural Components – Phosphoglycerides, sphingolipids, and steroids make up the basic structure of all cell membranes 4

17.
(1) FATTY ACIDS• Polyunsaturated Fatty Acids (MUFA) – are identified by position of the double bond nearest the methyl end (CH3) of the carbon chain; this is described as an omega number; – If PUFA has first double bond 3 carbons away from the methyl end = omega 3 FA – 6 carbons from methyl end = omega 6 FA 17

29.
CHEMICAL REACTIONS OF FATTY ACID• Esterification – Fatty acids react with alcohols to form esters and water 29

30.
CHEMICAL REACTIONS OF FATTY ACID• Acid Hydrolysis – Producing fatty acids from esters – Opposite of esterification• Saponification – Is the base-catalyzed hydrolysis of an ester – the product of this reaction, an ionized salt, is a soap • Have a long uncharged hydrocarbon tail and a negatively charged terminus (the carboxylate terminus 30

31.
CHEMICAL REACTIONS OF FATTY ACID• Saponification – Is the base-catalyzed hydrolysis of an ester – the product of this reaction, an ionized salt, is a soap • Have a long uncharged hydrocarbon tail and a negatively charged terminus (the carboxylate terminus), they form micelles that dissolve oil and dirt particles 31

38.
(2) GLYCERIDES• Neutral Glycerides – Produce after the esterification of glycerol with a fatty acid – Esterification may occur at one, two, or all three positions, producing: • Monoglycerides • Diglycerides • Triglycerides – most important and main storage form of lipids in man (adipocytes) 38

42.
(2) GLYCERIDES• Neutral Glycerides – There are no charges (+ or -) on these molecules – These long molecules readily stack with one another and constitute the majority of the lipids stored in the body’s fat cells – Primary function is to store energy • More energy-rich nutrients are consumed than are required for metabolic processes, much of the excess is converted to neutral glycerides and stored as TAG in fat cells 42

43.
(2) GLYCERIDES• Phosphoglycerides – Phospholipids – are group of lipids that are phosphate esters • The presence of the phosphoryl group results in a molecule with a polar head (the phosphoryl group) and a nonpolar tail (the alkyl chain of the fatty acid) 43

44.
(2) GLYCERIDES• Phosphoglycerides – Most abundant membrane lipids and derived from glycerol-3-phosphate – Contain acyl groups derived from long chain fatty acids at C-11 and C-2 of glycerol-3-phosphate – At C-3 the phosphoryl group is joined to glycerol by a phosphoester bond • Phosphatidate – simplest phosphoglyceride contains a free phosphoryl group 44